Voltage ride-through (VRT) and dynamic voltage support (DVS) are advanced functions of photovoltaic (PV) systems that are expected to improve future power system stability. Toward the improvement in system stability, it is valuable for power system operators (PSOs) to evaluate the effects of these functions. However, it is not straightforward to evaluate the amount of volt-ampere reactive (var) injection from PV systems because var injection depends on weather conditions and on the terminal voltages of the PV systems during voltage sag. In addition, it is equally important to analyze var support from distribution systems (DSs) to accurately determine the amount of var injection in a power system since numerous PV systems are connected to DSs. In this study, we evaluate the var support at a substation of a DS with PV during a voltage sag under various weather conditions. The var injection was analyzed for several time zones and seasons to consider a change in solar radiation. A numerical simulation was conducted based on IEEE 13 Node Test Feeder Model with PV systems. The results indicated that there is a large variation in var support depending on seasons or time zones with different solar irradiance.